One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,5)(6,8)(9,10)(11,15)(12,16)(13,17)(14,18)(19,23)(20,22)(21,24)(25,26)(27,35)(28,31)(29,33)(30,39)(32,37)(34,38)(36,40) involution — undirected(2,5)(6,7)(9,11,14,21)(10,15,18,24)(12,20,13,19)(16,22,17,23)(25,27,29,28)(26,31,33,35)(30,37,38,36)(32,39,40,34)(10,16)(11,19)(12,13)(17,18)(20,21)(22,23)(25,28,29,27)(26,32,33,40)(30,36,38,37)(31,34,35,39)(1,3,4,8)(2,6,5,7)(9,12,14,13)(10,16,18,17)(11,20,21,19)(15,22,24,23)(26,33)(31,35)(32,40)(34,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.